Eight members of Congress signed on to a January letter asking the heads of the Treasury and State Departments to take measures to intervene on behalf of a U.S.-owned company in the middle of a controversial dispute with Peru. Until now, Rep. Donald Payne, D-N.J., was the only known signatory of the letter sent to Secretaries Tim Geithner and Hlllary Clinton.

The missive, along with another from Rep. Spencer Bachus, came after the Renco Group, owned by billionaire mining magnate Ira Rennert, began a lobbying campaign spending more than $300,000 since November 2010 to influence Washington to help his troubled subsidiary, Doe Run Peru.

The letter was obtained from the Department of Treasury via a Freedom of Information Act request. The office of Rep. Payne has not released the letter despite requests by the Sunlight Foundation.

The seven other signatories, all Democrats, are:

Rep. Danny K. Davis, D-Ill.

Rep. Bobby Rush, D-Ill.

Rep. Lynn Woolsey, D-Calif.

Rep. Ed Towns, D-N.Y.

Rep. Gary Ackerman, D-N.Y.

Rep. Joe Crowley, D-N.Y.

Rep. Bill Pascrell, D-N.J.

The letter from Payne and his colleagues suggested that, if Doe Run Peru is expropriated from Peru, cutting off U.S. funding for Lima through the Inter-American Development Bank should be considered.

Doe Run Peru, which has been accused by environmental advocates of increasing pollution in a Peruvian mountain town and shirking their contractual obligations to clean up the area, faces bankruptcy proceedings and possible expropriation from Peru, a country with which the U.S. has a free trade pact.

Payne and Bachus received nearly identical response letters from Marisa Lago, the Assistant Secretary of the Treasury for International Markets and Development, in February.

In that letter, Lago wrote that the U.S. Embassy “has been in touch” with Lima regarding the issue. She also wrote that the trade pact was negotiated to allow for neutral arbitration of disputes.

Last month, Renco filed for arbitration under that pact, and in its notice of intent filed months ago, the mining company asked for as much as $800 million in damages from Lima. In that notice, Renco argued that Lima discriminated unfairly against it, among other claims.